The present disclosure relates to an automatic transmission that has a continuously variable speed change mechanism capable of changing the speed in a stepless manner while drivably coupling a driving source and wheels, for example.
Vehicular automatic transmissions that are installed with a continuously variable speed change mechanism, such as a belt-type continuously variable speed change mechanism (CVT), have become commonly available. For example, there is a known automatic transmission installed with a belt-type continuously variable speed change mechanism, which has a forward-reverse switching mechanism interposed between a primary pulley of the belt-type continuously variable speed change mechanism and an internal combustion engine. However, in this automatic transmission, holding pressure in the belt-type continuously variable speed change mechanism is necessary during both forward traveling and reverse traveling. Therefore, reduction in the burden on the internal combustion engine has been desired. Thus, an automatic transmission that uses a gear train that is exclusive to reverse traveling and fixes the speed ratio so as not to use the belt-type continuously variable speed change mechanism when a vehicle is traveling in reverse has been developed. For example, there is a known automatic transmission, including an input shaft that is drivably coupled to an internal combustion engine, an output shaft that is drivably coupled to wheels, a belt-type continuously variable speed change mechanism that is capable of coupling the input shaft and the output shaft, and the gear train that is capable of coupling the input shaft and the output shaft (see Japanese Patent Application Publication No. 63-57957). In this automatic transmission, the input shaft, a mechanism that connects/disconnects with the gear train, a forward clutch, and a primary pulley are disposed in order on a first axis. A secondary pulley, a reverse clutch, and the output shaft are disposed in order on a second axis that is parallel to the first axis.
In this automatic transmission, for forward traveling, the forward clutch is engaged and the input shaft and the continuously variable speed change mechanism are connected, the connecting/disconnecting mechanism is disconnected and the input shaft and the gear train are disconnected, and the reverse clutch is disengaged and the gear train and the output shaft is disconnected, so that the rotation of the input shaft is transmitted to the output shaft via the forward clutch and the continuously variable speed change mechanism. In this automatic transmission, for reverse traveling, the forward clutch is disengaged and the input shaft and the continuously variable speed change mechanism is disconnected, the connecting/disconnecting mechanism is connected and the input shaft and the gear train are connected, and the reverse clutch is engaged and the gear train and the output shaft are connected, so that the rotation of the input shaft is transmitted to the output shaft via the connecting/disconnecting mechanism, the gear train, and the reverse clutch. In this automatic transmission, the driving force can be transmitted without the intervention of the continuously variable speed change mechanism when a vehicle is traveling in reverse. Therefore, it is possible to eliminate the need for holding pressure and reduce the burden on the internal combustion engine.